Such electrical components have windings that are situated on cores. An example of a very high inductive load is the switching and engaging relay of a starter of an internal combustion engine of a motor vehicle.
In that regard, FIG. 1 shows a schematic view of a first exemplary embodiment of a conventional electrical component 11. Component 11 has a coil L2, R2, which is positioned around a core 12. Presently, for reasons of clarity and of congruence of the figures with the subsequent equations, many of the components shown in the figures are referred to by their characteristic values. For example, coil L2, R2 is referred to by its inductance L2 and its resistance R2.
In addition, electrical component 11 has a switch S2 for connecting coil L2, R2. Upon switching off coil L2, R2 with the aid of switch S2, a switch voltage US2 at switch S2 decreases. If, as in FIG. 1, no measures are taken to quench the inductive load of coil L2, R2 during the switching-off, then, in response to the switching-off, potential US2 decreases to the point where either an electric arc or an avalanche breakdown occurs there.
As a circuit diagram equivalent to this, FIG. 2 shows a schematic view of a second example of the electrical component 21. As in FIG. 1, electrical component 21 has a coil L2, R2 around core 22, as well as a switch S2. In FIG. 2, a Zener diode Dav is drawn to illustrate the effect of the arc or the avalanche breakdown explained with reference to FIG. 1. In addition, reference character PV in FIG. 2 shows the disruptive discharge power in response to switching off switch S2. The effect of the breakdown is normally very harmful to switching component 21 and may result in its destruction. Protective circuits are provided for this reason.
To this end, FIG. 3 shows a schematic view of a third example of a conventional electrical component 31. Electrical component 31 is constructed like electrical components 11 and 21 of FIGS. 1 and 2 and has, accordingly, a coil L2, R2 around a core 32, as well as a switch S2. In this context, electrical component 31 also has the Zener diode Dav described using FIG. 2. One form of a protective circuit is the free-wheeling diode 33 illustrated in FIG. 3. To increase the quenching voltage, this free-wheeling diode 33 is also connected in series to a Zener diode Dloesch. The higher the Zener voltage, the more rapidly the energy of the inductive load may be removed. However, the sum of the decrease in the diode voltage and the Zener voltage must be less than the breakdown voltage of switch S2, or else the destruction of component 31 is likely.
In addition, in the case of high amounts of energy and a short switching-off time, components such as relays, electromagnets or transformers have to be able to withstand very high power losses. This becomes especially critical when frequent switching operations occur. An example of frequently occurring switching operations is clocked or regulated activation of the electrical component.
Such regulated or current-regulated activation with the aid of two-step control or pulse-width modulation is used, for example, when a high drawing-in current, e.g., upon drawing in a magnet, or a high starting current, should initially flow, which should later be decreased, e.g., for holding a magnet. In the case of switching-on, a switch is completely switched through, whereas in the case of holding, alternating switching operations take place. A further, conventional option for performing such an action is division into a closing coil and a hold-in coil. To that end, FIG. 4 shows a schematic view of a fourth exemplary embodiment of a conventional electrical component 41. In this context, electrical component 41 has two coils L1, R1 and L2, R2, which are wound on a common core 42. A first switch S1 is provided for connecting first coil L1, R1. Analogously, a second switch S2 is provided for connecting second coil L2, R2. The voltages at switches S1 and S2 that decrease during the switching operation are referred to as US1 and US2. For example, first coil L1, R1 may be configured as a hold-in coil. Second coil L2, R2 may then be configured as a closing coil. In this context, closing coil L2, R2 is designed in such a manner, that the required, rapid drawing-in is implemented at currents of closing coil L2, R2 that are typically relatively high. Subsequently, a switchover may be made to hold-in coil L1, R2, which has a markedly lower power requirement (R1>>R2). A component such as in FIG. 4 is known, for example, from conventional starter relays.
In addition, capacitors are used as rapid quenching elements or storage elements. Therefore, on one hand, the energy may be removed rapidly from the magnetic circuit, and on the other hand, energy for boosting may be made available for a short response time during closing.
Since, in certain cases, inductive loads may store very high amounts of energy, e.g., up into the range of 1 Joule for starter relays, the degree of complexity and the cost of protective circuits may become relatively high.